1. Field of the Invention
The present invention relates to an art of adhering a thin film and particularly relates to a more effective art in which a thin film, whose length corresponds to that of a base plate is adhered to the thin film adhering side of the plate.
2. Background
In a conventional process of manufacturing a printed circuit board for an electronic appliance such as a computer, a laminated film is adhered to the surface of a base plate for a printed circuit. The laminated film consists of a photosensitive resin layer and a light-transmissive resin film. The photosensitive resin layer is adhered directly to the surface of the base plate. The light-transmissible resin film is provided on the photosensitive resin layer to protect it. The laminated film is adhered to the base plate by a thin film adhering apparatus as described in the Japanese Patent Application (OPI) No. 117487/88 (the term "OPI" as used herein means an "unexamined published application") made by the present Applicant.
The procedure of adhering the laminated film to the base plate is as follows. The leading edge portion of the base plate is first conveyed to a thin film adhering position by a base plate conveyance mechanism and stopped in that position. The leading edge portion of the continuous laminated film supplied from a thin film feed roller is then suctioned against a main vacuum suction plate which is a thin film feed member. A thin film temporary adhering member is provided at the leading end of the main vacuum suction plate facing the thin film adhering position so that the leading edge portion of the laminated film is suctioned onto the temporary adhering member. The temporary adhering member has suction holes communicating with a vacuum suction system for suctioning the laminated film. A heater for temporarily adhering the leading edge portion of the laminated film is provided in the temporary adhering member.
The main vacuum suction plate and the thin film temporary adhering member are moved to the vicinity of the thin film adhering position or the surface of the leading edge portion of the base plate. The leading edge portion of the laminated film is then brought into contact with the surface of the leading edge portion of the base plate, and temporarily adhered thereto, under heat and pressure by the temporary adhering member. Thereafter, the main vacuum suction plate and the thin film temporary adhering member no longer apply suction and are moved away from the thin film adhering position. At that time, the leading edge portion of the laminated film does not deviate from the thin film adhering position because the leading edge portion is already temporarily adhered to the surface of the base plate. A heat and pressure adhering roller is thereafter moved to the thin film adhering position so that the temporarily adhered portion of the laminated film is pressed by the roller. The roller is then rotated as the laminated film remains pressed by the roller, so that the whole laminated film is gradually adhered to the surface of the base plate, under heat and pressure, while the base plate is being conveyed.
The laminated film is automatically supplied to the thin film adhering position by the rotation of the heat and pressure adhering roller and the conveyance of the base plate. During the heat and pressure adhering of the laminated film of the surface of a base plate, the trailing edge of the base plate is detected to generate a detection signal in accordance with which the continuous laminated film is cut at the trailing edge portion thereof. For that reason, the length of the cut-off laminated film corresponds to that of the base plate extending in the direction of the conveyance thereof. Cutting the laminated film is performed by moving a disk-shaped cutting member across the direction of the supply of the laminated film as the film is held at the trailing edge portion thereof by the suction of an auxiliary vacuum suction plate provided at the feed passage for the laminated film. The trailing edge portion of the laminated film cut as mentioned above is held by the suction of a thin film trailing edge portion suction member so that an appropriate tensile force is applied to the laminated film. Simultaneously, the trailing edge portion of the laminated film is guided to the trailing edge portion of the base plate so that the trailing edge portion of the film is adhered to the surface of the trailing edge portion of the base plate under heat and pressure, by the heat and pressure adhering roller. The base plate with the laminated film adhered thereto by the thin film adhering apparatus as described above is conveyed to an exposure apparatus installed next thereto. Such a thin film adhering art, in which a portion of a laminated film is temporarily adhered to, a base plate for a printed circuit and the laminated film is thereafter completely adhered to the base plate, under heat and pressure, was disclosed in the West German Patent DE 3334009 C2 and the Japanese Patent Application No. 49169/87.
The above-mentioned adhering process includes the step of cutting off the laminated film at the trailing edge side thereof during the adhering of the laminated film under heat and pressure. The cutting of the laminated film is carried out by a cutting member as described above. When cutting the laminated film, chips produced from the thus cut laminated film are scattered to contaminate the surroundings. The scattered chips deposit on the surfaces of a printed circuit board and the laminated film which are just to be adhered together under heat and pressure. Therefore, in many cases, those portions on which the chips deposit are defective, thus increasing the number of imperfect printed circuit boards. This results in a problem that the yield of the adhering process is lowered.